Medical referencing devices, which are used, for example, in knee prosthetics to make it easier for a surgeon to implant an artificial knee joint, are known.
The referencing device comprises the marking device with marking elements arranged rigidly relative to one another (so-called “rigid body”) whose movement in space is tracked by a navigation system. To achieve as high an accuracy as possible, the marking device is screwed with a fastening device usually a bone screw, to the femur bone or to the tibia bone and thereby firmly fixed to it. However, this results in an intervention with a not inconsiderable degree of invasiveness about which some surgeons and patients have reservations.
To reduce the invasiveness, it is known to fix rigid bodies on a sleeve placed around the femur (in this case, thigh) or the tibia (in this case, lower leg) or to mount them on a plate placed on the femur or the tibia, which is fixed with bands to the respective body part. The sleeve comprises or forms a fastening device of the kind mentioned at the outset with a support body extending over a surface, which can undergo deformation from its originally planar shape and be adapted to the contour of the body part (for example, the femur or the tibia), so as to enable a positive fit on the body part.
Support bodies, which can be adhesively connected to the body part and to which the marking device is fixed, are also known.
With such noninvasive fastening devices, the problem occurs in practice that movements of the skin and muscles and soft tissue displacements, in particular, when movement of the body part in space is to be detected, are transmitted via the support body to the marking device. The accuracy of the position data of the marking device—and hence of the body part—on which the navigation-supported operation is to be based, is thereby impaired.
It would also be desirable to preoperatively and postoperatively detect patient data with a medical navigation system via a fastening device noninvasively attachable to the body part. Surgery times can thereby be reduced because data required therefore are already available preoperatively and need not first be determined intraoperatively. The success of the operation can be easily monitored postoperatively. In both cases, ionizing imaging procedures otherwise used, such as X-ray or CT, can be replaced.
An object underlying the present invention is to provide a generic fastening device, a referencing device and an instrumentation, with the use of which the noninvasively obtained position data have a higher accuracy.